JP4586987B2 - X-ray CT system - Google Patents

Description

  The present invention relates to an industrial X-ray CT apparatus.

  For example, X-ray images are frequently used to inspect whether there is a nest inside an aluminum casting or the like. While simple fluoroscopy has the advantage of high throughput, it is difficult to accurately and quantitatively grasp the position and shape of the nest, and generally the skill of an operator who determines whether the nest is good or bad by observing a fluoroscopic image It depends heavily on the degree.

  In contrast, an X-ray CT apparatus can observe a tomographic image, and thus has an advantage that the position and size of the nest can be accurately obtained. However, CT imaging generally requires a considerable amount of time for imaging and has a problem of low throughput. Also, if you want to cover the whole image of the subject with a single CT scan, if the measurement area (scanning area) is sufficiently large, it is only necessary to pay attention to the arrangement of the subject as long as it is in the field of view. However, since the measurement area is large, not only the measurement time is lengthened, but also an X-ray detector having a large light receiving area is required, leading to an increase in cost. In addition, since the spatial resolution is reduced above all, there is a problem that minute nests and defects cannot be detected.

  In order to increase the resolution, the subject is locally enlarged and imaged, but in this case, the field of view becomes small and the entire image cannot be observed. When performing CT imaging by locally enlarging the subject, it is necessary to move the desired position on the subject to the measurement region of the X-ray CT apparatus. For such movement of the subject, a configuration in which an xy table or the like is usually mounted on a rotary stage that rotates the subject is employed. When positioning the subject, the operator operates the xy stage while viewing a fluoroscopic image of the subject (see, for example, Patent Document 1).

2. Description of the Related Art Conventionally, a chucking device provided on a robot's hand unit is rotated by a robot's drive shaft as a device that positions and rotates a subject using a structure other than a rotary stage and an xy stage. (For example, refer to Patent Document 2). That is, in the technique described in this publication, as shown in FIG. 4, the shape of the subject W is formed at the tip of an arm 43a having a plurality of joints adjacent to the X-ray generator 41 and the X-ray detector 42. A multi-axis robot 43 including a chucking device 43b that is appropriately replaced in accordance with the rotation of the chucking device 43b and a rotation mechanism 43c that rotates the chucking device 43b around its central axis is disposed. After chucking the subject W on the carry-in stage 44 by the chucking device 43b 43, the subject W is transported and positioned at a preset position between the X-ray generator 41 and the X-ray detector 42. Then, the subject W is rotated by the rotation mechanism 43c, and CT imaging is performed. The object W after imaging is transported to the unloading stage 45 and released while being chucked by the multi-axis robot 43.
JP 2005-308633 A JP 2005-221460 A

  By the way, in the inspection of an aluminum casting, it is necessary to observe all areas of the specimen without omission in the first lot, but when the production process becomes stable, it is usually not necessary to observe all areas. It is desirable that the same subject can be flexibly adapted to the entire CT observation, partial CT observation, fluoroscopic observation alone, etc., according to the situation, so that the situation at the production site can be quickly handled.

  In the method of changing the position of the subject by mounting the xy stage on the rotary stage, the operator moves the xy stage while viewing the fluoroscopic image of the subject in order to obtain a local enlarged tomographic image in inspection of an aluminum casting or the like. The operation to operate is not easy.

  Further, in the conventional proposed technique using a multi-axis robot, the chucking device is provided in the immediate vicinity of the rotation mechanism, and the positional relationship and posture between the rotation mechanism and the chucking device are constant. Although there is no problem when slicing the same position, it is difficult to handle when it is necessary to obtain a tomographic image along an arbitrary cutting direction at an arbitrary position on the object, such as inspection of an aluminum casting. It is. That is, in the technique of Patent Document 2, the rotating shaft and the chucking device are substantially integrated, and once the subject is chucked, CT imaging centered on a location away from the position on the rotating shaft. In addition, since the chucking device cannot be tilted with respect to the rotation axis, the angle of the slice plane cannot be changed. In order to obtain tomographic images at a plurality of observation positions or slice angles, it is necessary to rechuck the subject.

  The present invention is capable of quickly changing the observation position on the premise that a minute defect that causes a quality problem can be observed by taking a magnified image to some extent, for example, inspection of an aluminum casting. To provide an X-ray CT apparatus capable of easily changing the setting of an observation position and an observation mode (such as fluoroscopy or CT) without having to re-chuck the subject in moving the subject for That is the issue.

  In order to solve the above-described problems, the X-ray CT apparatus of the present invention has a focal point of the X-ray generator and the center of the X-ray detector between the X-ray generator and the X-ray detector arranged to face each other. A subject stage that rotates the subject around a rotation axis that is orthogonal to the connecting line is provided, and using the X-ray projection data of the subject that is captured at every minute rotation angle around the rotation axis, In an X-ray CT apparatus that reconstructs a tomographic image of a subject along a plane orthogonal to a rotation axis, the subject stage is supported by a rotation mechanism that is rotated about the rotation axis, and the rotation mechanism. It is characterized by being constituted by an articulated robot that holds a subject and changes its position and posture (claim 1).

  Here, in the present invention, it is possible to employ a configuration (claim 2) that uses the drive shaft closest to the base among the plurality of drive shafts of the articulated robot as the rotation mechanism.

  Further, in the present invention, at least two optical cameras for photographing the position where the X-ray optical axis from the X-ray generation device and the rotation axis intersect from different directions are displayed, and images from the respective optical cameras are displayed. The structure (Claim 3) provided with the display means to perform can be used suitably.

  In the present invention, rotation for CT imaging is given in a state where the subject is gripped using a robot. However, the multi-joint robot that grips the subject is supported on a rotation mechanism, so that the rotation can be performed. The object can be freely moved and tilted with respect to the axis to solve the problem.

  That is, in the present invention, each articulated robot that holds the subject is rotated by the rotation mechanism, so that the subject is moved to an arbitrary position and posture with respect to the rotation axis of the rotation mechanism by driving the articulated robot. Can be moved. As a result, CT imaging can be performed at an arbitrary position and an arbitrary slice angle without re-holding the subject. And since the position and posture are changed while the subject is gripped by the articulated robot, it is possible to quickly move the subject to a desired position and posture by setting a plurality of positions and postures of the subject by teaching. It becomes possible.

  Moreover, even if the drive shaft closest to the base of the articulated robot is used as a rotation mechanism for rotating the subject during CT imaging as in the invention according to claim 2, the same effect as described above can be obtained.

  Then, as in the invention according to claim 3, the position where the rotation axis of the rotation mechanism and the X-ray optical axis intersect is photographed from different directions by at least two optical cameras, and the image is displayed on the display. If it comprises, for example at the time of teaching, it can grasp | ascertain intuitively which position and the attitude | position of the subject are with respect to CT imaging area | region (scan area | region).

  According to the present invention, the articulated robot is supported on the rotation mechanism, and the position and posture of the subject with respect to the rotation axis are changed by the articulated robot, so that any position on the subject can be changed to any posture. For example, it can be used for inspections such as whether or not there is a nest inside an aluminum casting, and the observation position and slice angle can be changed without re-gripping the subject. Work becomes easy.

  Also, in the inspection of aluminum castings as described above, if the position where the nests are likely to be generated can be grasped in the first lot inspection, etc., the subject can be quickly moved to the required position / posture by teaching. And the inspection work can be facilitated.

  Then, as in the invention according to claim 3, when the position where the rotation axis and the X-ray optical axis intersect is photographed from different directions with at least two optical cameras and displayed on the display, a photographing region (scan region) Therefore, it is possible to intuitively grasp the position and posture of the subject, and manual inspection work and teaching work of the articulated robot are facilitated.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an embodiment of the present invention, and is a diagram illustrating a schematic plan view of a mechanical configuration represented by seeing through a ceiling plate of a protection box 1 and a block diagram representing a system configuration. . FIG. 2 is a perspective view showing a main mechanical configuration in the protection box 1 according to the embodiment of the present invention.

  An X-ray generator 2 and an X-ray detector 3 are disposed in the protection box 1 so as to face each other in the horizontal direction, and a vertical articulated robot 4 is disposed adjacent to these. The X-ray generator 2 generates cone-beam X-rays in the horizontal direction. The X-ray detector 3 is, for example, a two-dimensional image tube.

  The vertical articulated robot 4 is a known 5-axis vertical articulated robot including an arm portion 4b on a base 4a and a hand portion 4c for gripping a subject W at the tip of the arm portion 4b. The arm part 4b can be rotated around a vertical rotation axis R with respect to the base 4a. The rotation axis R intersects the line connecting the X-ray focal point of the X-ray generator 2 and the center of the light receiving surface of the X-ray detector 3, that is, perpendicular to the X-ray optical axis L. The base 4 a of the vertical articulated robot 4 is placed on a linear motion mechanism 5 that moves parallel to the X-ray optical axis L.

  The protection box 1 is provided with a door 1a, and a work table 6 is disposed outside the door 1a. The vertical articulated robot 4 grasps the subject W on the work table 6 with the hand 4c through the door 1a and carries it into the protective box 1 and, as will be described later, the X-ray generator 2 and the X-ray detector 3 as described later. Positioning is performed during this period, and an operation corresponding to the selected mode is performed. Among these modes, in the CT imaging mode, the subject W is rotated while irradiating X-rays, and X-ray projection data is taken in at every predetermined rotation angle. A rotation axis R that rotates the arm portion 4b with respect to the base 4a of the four is utilized.

  In the protection box 1, CCD cameras 7 and 8 are provided for photographing the vicinity of the position where the rotation axis R and the X-ray optical axis L intersect from the vertical direction and the horizontal direction, respectively (in FIG. The camera 7 is not shown). Video signals from the CCD cameras 7 and 8 are taken into the personal computer 10 and displayed on the display 11 as an appearance image.

  Further, the pixel output of the X-ray detector 2 described above is also taken into the personal computer 10 to display an X-ray fluoroscopic image on the display 11 and tomographic image reconstruction by back projection installed in the personal computer 10. Provided for calculation.

  FIG. 3 shows a configuration example of the screen of the display 11. In this example, an X-ray image display area Px for displaying an X-ray fluoroscopic image or a tomographic image, and external image display areas Pc1 and Pc2 by two CCD cameras 7 and 8 are provided. A condition setting area Sx, a setting button Br for teaching mode of the vertical articulated robot 4, a CT imaging start button Bs, image brightness and contrast setting buttons Bb, Bc, and the like are provided.

  The tube voltage and tube current of the X-ray generator 2 are supplied from the X-ray controller 12, and the X-ray controller 12 is placed under the control of the personal computer 10. The vertical articulated robot 4 is controlled by a robot controller 13, which is also under the control of the personal computer 10. Further, the linear motion mechanism 5 is operated by a drive signal supplied from the driver 14, and the driver 14 is also under the control of the personal computer 10.

  An operation command can be given to the robot controller 13 and the driver 14 by operating the operation unit 15, and the robot 4 can be taught by operating the operation unit 15.

  Next, the operation of the embodiment of the present invention having the above configuration will be described. By operating the operation unit 15, a manual fluoroscopic imaging mode, a manual CT imaging mode, a CT imaging teaching mode, and an automatic CT imaging mode can be selected.

  First, in the manual fluoroscopic imaging mode, when a command to that effect is given by operating the operation unit 15, the door 1 a is opened, and the vertical articulated robot 4 grips the subject W on the work table 6 to protect the protection box 1. Then, the door 1a is closed by positioning it at a preset position between the X-ray generator 2 and the X-ray detector 3. While irradiating X-rays in this state, while viewing the X-ray fluoroscopic image displayed on the display 11, the vertical articulated robot 4 is driven by the operator's manual operation, and the subject W is moved up and down, left and right, or tilted. Or moving it back and forth to change the perspective magnification, and the operator determines whether there is a defect such as a nest. At this time, since the appearance image of each CCD camera 7 and 8 is displayed on the display 11 together with the X-ray fluoroscopic image, the operator intuitively grasps which position is viewed from which direction. Can do.

  In the manual CT imaging mode, after setting or confirming imaging conditions (imaging time, etc.), the subject W is held by the vertical articulated robot 4 in the same manner as described above, and the X-ray generator 2 and the X-ray detector 3 are set. The vertical articulated robot 4 is driven by an operator's operation to position and fix the subject W at a required position and posture, and then a CT imaging start command is given. The position and orientation of the subject W can be determined while viewing the fluoroscopic image of the subject W and the external appearance image from two directions, and intuitively grasp the position of the tomographic image to be taken. be able to. When it is desired to change the enlargement ratio, the linear motion mechanism 5 is driven to move the vertical articulated robot 4 holding the subject W in the X-ray optical axis L direction.

  At the time of CT imaging, the vertical articulated robot 4 rotates the arm unit 4b with respect to the base 4a around the rotation axis R while holding the subject W with the hand unit 4c, and rotates the arm at every minute rotation angle. X-ray projection data of the specimen W is captured. In this CT imaging, if the arm 4b can be rotated 360 ° or more with respect to the base 4a, it is rotated 360 °. If this is not possible, the image can be reconstructed by rotating it by 180 ° + the opening angle of the X-ray beam (half scan).

  In the CT imaging teaching mode, the imaging locations are registered in advance in the manual CT imaging mode described above. By this registration, in the automatic CT imaging mode, the vertical articulated robot 4 automatically moves the subject W in the order of registration, and the CT imaging is sequentially performed.

  In the embodiment of the present invention described above, the X-ray generator 2 is, for example, HS225, the maximum tube voltage is 225 kV, 320 W, the focal point is 0.5 mm, and the X-ray detector 3 is a 9-inch image tube multi-channel. This is a type, the field of view can be switched, the horizontal distance between the focal point of the X-ray generator 2 and the X-ray detector 3 is 1000 mm, and the subject W is centered, that is, the rotational axis R at a position 500 mm from the X-ray focal point. , The imaging magnification is double, and the field of view is 140 mm, the CT imaging possible area is the area indicated by A in FIG. 2, and its diameter is 70 mm and the height is 70 mm. It becomes an area. When reconstructed with 500 pixels, one pixel is about 0.14 mm. Therefore, a defect of about 0.5 mm can be sufficiently detected.

  According to the embodiment of the present invention described above, the rotation axis R that rotates the subject W during CT imaging uses the drive axis that rotates the arm portion 4b relative to the base 4a of the vertical articulated robot 4. In addition, since the hand portion 4c that holds the subject W can be freely displaced and tilted with respect to the rotation axis R, a tomographic image along an arbitrary direction at an arbitrary position of the subject W can be obtained. At the same time, compared with the case where the xy stage is mounted on the rotary stage and positioned, the operation is easy even in manual operation, and in automatic CT imaging, each joint moves simultaneously by teaching and quickly registers. The throughput is greatly improved since the position / posture is determined.

  In the above embodiment, the rotation drive axis of the arm unit with respect to the base of the vertical articulated robot is used as the rotation axis R for rotating the subject W during CT imaging, but the present invention is limited to this. Alternatively, a separate rotation mechanism may be provided, and the vertical articulated robot may be disposed thereon.

  In the above embodiment, the vertical articulated robot is mounted on the linear motion mechanism that moves along the X-ray optical axis in order to change the imaging magnification (magnification ratio). Is not necessary.

FIG. 2 is a configuration diagram of an embodiment of the present invention, and is a diagram illustrating a schematic plan view of a mechanical configuration that is seen through the ceiling plate of the protection box 1 and a block diagram that shows a system configuration. It is a perspective view which shows the main mechanical structures in the protection box 1 of embodiment of this invention. It is explanatory drawing of the structural example of the display screen of the indicator 11 of embodiment of this invention. It is explanatory drawing of a structure of the X-ray CT apparatus using the conventional robot.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Protective box 1a Door 2 X-ray generator 3 X-ray detector 4 Vertical articulated robot 4a Base 4b Arm part 4c Hand part 5 Linear motion mechanism 6 Work stand 7, 8 CCD camera 10 Personal computer 11 Display 12 X-ray controller 13 Robot controller 14 Driver 15 Operation unit W Subject

Claims (3)

Between the X-ray generator and the X-ray detector arranged opposite to each other, the subject is rotated about a rotation axis orthogonal to a line connecting the focal point of the X-ray generator and the center of the X-ray detector. A tomographic image of a subject along a plane perpendicular to the rotation axis is reconstructed by using X-ray projection data of the subject provided at every minute rotation angle centered on the rotation axis. X-ray CT apparatus
The subject stage is composed of a rotation mechanism that is rotated about the rotation axis, and an articulated robot that is supported by the rotation mechanism and that grips the subject and changes its position and posture. X-ray CT apparatus that is characterized.   2. The X-ray CT apparatus according to claim 1, wherein a drive shaft closest to a base among a plurality of drive shafts of the articulated robot is used as the rotation mechanism.   The apparatus includes at least two optical cameras that photograph the positions where the X-ray optical axis from the X-ray generation device and the rotation axis intersect from different directions, and display means for displaying images from the respective optical cameras. The X-ray CT apparatus according to claim 1 or 2, wherein

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